Thermal Protection and Controls

Official Microtherm GmbH Agent for UK and Ireland
T +44(0) 20 3490 4299 F +44(0) 20 3163 0674 E

CD79 Thermal Cutout/Switch

CD79

CD79

DESCRIPTION
The CD79 device is a thermal cutout, providing over-temperature protection. It is an alternative to Klixon 17AM thermal switch. A thermally sensitive bimetal snap-element switches when it reaches a pre-set response temperature or a fixed current level, opening the circuit. Current flows through the bimetal element, giving a combination of temperature- and current- protection. Heat transfer occurs from all sides through convection, radiation or conduction in gaseous or solid media. The rhomboid shape conducts heat directly onto the bimetal snap-element, thus allowing its use as a surface temperature cutout.
 
APPLICATIONS
Over-temperature protection and, under certain conditions, temperature control of electrical machinery and equipment.
 
INSTALLATION NOTES
When installing the cutout, good heat transfer must be ensured. The heat sensitive side of the switch (the base) should be positioned on the heat source. Heat-conducting paste or lacquer improves heat transfer. Please note that in the standard version the cutout has an electrically live housing, and that when electrically insulated, the cutout’s effective switching temperature can be affected by reduced heat transfer through the insulation. This should be borne in mind when selecting the appropriate temperature setting.
With single phase motors, the cutout should switch the mains supply. It will then switch off the motor directly in the case of undesirable heating. A short circuit in the motor will also be broken safely if the resulting current is higher than the cutout rating. In 3-phase motors, the current should not be switched directly via the mains supply. The cutouts are installed in the windings and connected in series with the magnetic coil of the contactor. The cutouts are connected either singly or collectively via the motor’s terminal block to allow connection into the control circuit.
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